Boundary Mobilities in Binary Al-Mn Alloys

Abstract:

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This paper described new characterization methods and data to quantify the influence of
solute atoms on grain boundary and sub-grain boundary mobilities in Al-Mn alloys with a view to
their integration into recovery and recrystallization modelling.
Detailed SEM measurements of grain boundary mobilities during recrystallization have been made
by in-situ annealing experiments on cold deformed Al – 0.1 and 0.3wt.% Mn binary alloys. Stored
energies are estimated from the sub-grain sizes and misorientations and the boundary velocities
directly measured in the temperature range 200-450°C. It is shown that in many cases good
agreement with the Cahn, Lücke, Stüwe model for solute drag is obtained, e.g. the activation
energies are intermediate between those of boundary and volume solute diffusion. Some particular
cases of rapid growth occur in Al-0.1%Mn indicating boundary breakaway from solute clouds.
A complementary study of sub-grain boundary mobilities has started on the same alloys; in this
case the average mobilities are estimated from FEG-SEM growth data for the average sub-grain
size for temperatures in the range 150-300°C. The results are compared with some previous data on
Al-Si and show similar rates.